Method of making alpha, beta-dimethylenesuccinonitrile



atented Sept. 6, 1949 METHOD MAKING ALPHA, BETA-DI- METHYLENESUCCINONITRILE Erhard J. Prill, Cresskill, N. J., assignor to United States Rubber Company, New York, N. Y., a corporation of New Jersey No Drawing. Application August 29, 1947, Serial No. 771,378

This invention relates to a method of preparing a,;8-dimethylenesuccinonitrile, which is a compound useful both as a polymerizable unsaturated monomer and as an intermediate for the synthesis of other compounds. More particularly it relates to the preparation of a,,s-dirnethylenesuccinonitrile from a 2,3-dicyano-3-buten-2-yl ester of a lower monocarboxylic acid. In another aspect it relates to an improved method of preparing a,,c-dimethylenesuccinonitrile from lower monocarboxylic acid diesters of 2,3butanedione bis-cyanohydrin.

I have discovered that a,fl-dimethylenesuccinonitrile can be prepared by the thermal decomposition of an ester of 2,3-dicyano-3-buten- 2-01 with a lower carboxylic acid containing from one to seven carbon atoms, as fllustrated by the following equation;

in which R is selected from the group consisting of hydrogen, phenyl, and alkyl groups having from one to six carbon atoms, examples of which are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, secondary butyl, tertiary butyl, any of the amyl radicals including n-amyl, active amyl, isoamyl, secondary amyl, neopentyl, secondary isoamyl, tertiary amyl, any of the hexyl radicals including n-hexyl, isohexyl, etc.

In accordance with the present invention the 2,3-dicyano-3-buten-2-yl ester of the monocarboxylic acid is heated at an elevated temperature and for a time such as to efiect thermal decomposition of the ester to form the desired :,[3-(11- methylenesuccinonitrile which is recovered from the reaction effiuent. The reaction is preferably carried out at a temperature of from 400-500 C. and for a contact time of from to 30 seconds. The vapors of the 2,3-dicyano-3-buten-2-yl ester, either by itself or in admixture with a suitable unreactive solvent which facilitates introduction of the ester, e. g. acetone, may be continuously passed through a reactor, such as a reaction tube, which is maintained at a temperature from 400-500 C., at such a rate that contact times of from 15 to 30 seconds are attained. The reaction can be conducted at atmospheric pressure. Alternatively the reaction can be conducted at reduced pressures and/ or in the presence of an inert diluent such as nitrogen or acetone vapor. The hot gaseous effluent may be treated in any suitable manner to recover the a,p-dimethylenesuccinonitrile therefrom. This may conveniently be ac- 5 Claims. (Cl. 260-4653) complis'hed by condensing the hot efiiuent gas, removing any diluents present, and isolating and purifying the a,;8-dimethylenesuccinonitrile by fractional distillation of the residue.

As a result of my discovery ays-dimethylenesuccinonitrile can be prepared in an improved manner from lower monocarboxylic acid diesters of 2,3-butanedio-ne bis-cyanohydrin by a two-stage process, the first stage of which comprises heating the lower monocarboxylic acid diester of 2,3- butanedione bis-cyanohydrin in a reaction zone at an elevated temperature and for a time such as to effect thermal decomposition of the diester to form the 2,3-dicyano-3-buten-2-yl ester of the monocarboxylic acid (as disclosed and claimed in my co-pending application, Serial No. 769,535, filed Aug. 19, 1947, now Patent No. 2,446,167, granted August 3, 1948) The monoester is recovered from the effluent and is thereafter thermally decomposed in a separate reaction zone in the second stage according to the present invention to form a,B-dimethylenesuccinonitrile, which is recovered from the second stage reaction eflluent in the manner described above. When employing such a two-stage process for the preparation of u,13-dimethylenesuccinonitrile from the diester, I prefer to use in the first thermal decomposition step a temperature of from 400 to 500 C. and a contact time of from 0.2 to 5 seconds, and in the second thermal decomposition step a temperature of 400 to 500 C. and a contact time of from 15 to 30 seconds. The over-all yield of a,fi-dlmethylenesuccinonitrile from the diester is considerably better by the use of my two-stage process than by a single stage process; under favorable circumstances being as much as a hundred per cent higher.

The following example discloses my invention in more detail. All parts are by weight.

Example The reaction vessel, a 40-inch length of 30 mm. Pyrex tubing packed with 3-8 mesh quartz chips and equipped with a heater, is maintained at 435 C. while 50 parts of 2,3-dicyano-3-buten- 2-yl acetate are passed through it with an average contact time of approximately 25.0 seconds (based on the volume of free space in the tube).

The hot effluent gases are condensed in a receiver cooled by dry ice and containing 0.1 part of hydroquinone as a polymerization inhibitor. Fractional distillation of the condensate yields a,fi-dimethylene-succinonitrile, which boils at approximately C./8 mm. with considerable sublimatlon.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

1. A method of making u,fl-dimethy1enesuc cinonitrile which comprises heating a 2,3-dicyano-3-buten-2-y1 ester of a monocarboxylic acid, having the structural formula ON CN where R is selected from the groub-etiisiiihig bi hydrogen, alkyl groups havingirom one to six carbon atoms and phenyl, for atimepf from 15 116130. seconds in a reaction zone maintained at a teminula for an average contact time of approximately 25 seconds in a reaction zone maintained at a temperature of 435 C., removing the products from the reaction zone, and recovering a,,8-dimety1enesuccinonitrile therefrom.

A methodas recitedjin claim 1 wherein said heatin stp is-conductedat atmospheric pressure. a ,,5. A method of making afi-dimethylenesuccinonitrile which comprises heating a lower monocarboxyli'c acid diester of 2,3-butadiene biscyanohyd'ri'ri for a time of from 0.2 to 5 seconds in a reaction zonernaintained at from 400 to 500 C., r in the reaction effluents a 2,3-diy1 ester of a monocarboxylic acid having the structural formula ON ON oHi=('Jt -oH,

- CO-R whereBs s ql q fi i fi h group o tin of hydrogen, alkylgroups having from one to six carbon atornsland phenyl, heating said 2,3-dicyanpa 3 butene; ;yl ester for atirne of from 15 to. secondsin a separate reaction zone maintained at i mp rati reci 3 11409 to 50 0., an co ering 43;dimethylenesuccinonitrile from the re-V sultingreaction eifiuent.-

ERHARD J. PRILL. ana ram 'CIiiED The following references are of record in the file of this patent nNI'TEIj STATES PATENTS Number 1. VNarne I Date 2,328,890 Clifford etal. Sept. 7, 1943 2,444,882 Tawney July '6', 1948 Certificate of Correction Patent N 0. 2,480,961 September 6, 1949 ERHARD J. PRILL It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 36, for that portion of the structural formula reading CI-I C read 0H =0; column 4, line 4, for -dimetyleneread -d'imethyZene-;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 3rd day of January, A. D. 1950.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents. 

